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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 16 Jan 2019 17:34:01 +1200
Message-ID: <CAHk-=wjqkbjL2_BwUYxJxJhdadiw6Zx-Yu_mK3E6P7kG3wSGcQ@mail.gmail.com>
Subject: Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged
To:     Andy Lutomirski <luto@amacapital.net>
Cc:     Josh Snyder <joshs@netflix.com>,
        Dominique Martinet <asmadeus@codewreck.org>,
        Dave Chinner <david@fromorbit.com>,
        Jiri Kosina <jikos@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Jann Horn <jannh@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Michal Hocko <mhocko@suse.com>, Linux-MM <linux-mm@kvack.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>
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On Wed, Jan 16, 2019 at 5:25 PM Andy Lutomirski <luto@amacapital.net> wrote:
>
> Something like CAP_DAC_READ_SEARCH might not be crazy.

I agree that it would work. In fact' it's what Jiri's patch basically
did. Except Jiri used CAP_SYS_ADMIN instead.

But that then basically limits it to root (or root-like with
capability masks), which is quite likely to not work in practice all
that well. That's why I wanted to find alternatives.

*Very* few people want to run their databases as root.

Jiri's original patch kind of acknowledged that by making the new test
be conditional, and off by default. So then it's a "only do this for
lockdown mode, because normal people won't find it acceptable".

And I'm not a huge fan of that approach. If you don't protect normal
people, then what's the point, really?

              Linus